Wobble plate pumps typically include pistons that move in a reciprocating manner within corresponding pumping chambers. The pistons are generally coupled to a wobble plate and are reciprocated by a cam that is rotated by a motor or other driving device. The reciprocating movement of the pistons pumps fluid from a fluid inlet to a fluid outlet of the pump. The pistons of the pump are often coupled to a diaphragm that is positioned between the wobble plate and the pump chambers. In some such pumps, each one of the pistons is an individual component separate from the diaphragm, requiring numerous components to be manufactured and assembled. A convolute is sometimes employed to connect each piston to the diaphragm, so that the pistons can reciprocate and move with respect to the remainder of the diaphragm.
Some conventional pumps (including wobble plate pumps) have a bypass port which allows for fluid entering the pump to bypass the pumping chambers when the pressure at the outlet side of the pump is high. This helps to reduce the “water hammering” noise that occurs when a downstream valve is limiting the flow rate but the pump is still trying to push water at its nominal flow rate. However, the bypass of fluid comes at the expense of pump efficiency. It also requires the design and manufacture of a separate fluid path.
Many conventional pumps include a controller or switch for controlling the on-off state of the pump, especially for shutting off the pump in response to increased pressure (i.e., a shut-off pressure). For example, an actuator of a mechanical switch is typically positioned in physical communication with the fluid in the pump. When the pressure of the fluid exceeds the shut-off pressure, the force of the fluid moves the actuator to open the pump's power circuit to turn off the pump.
Mechanical pressure switches may be susceptible to breakdown due to overuse. For example, during repeated opening and closing of the pump's power circuit, arcing and scorching often occurs between the contacts of the switch. Due to this arcing and scorching, an oxidation layer forms over the contacts of the switch, and the switch will eventually be unable to close the pump's power circuit. Repeated switching may occur because mechanical pressure switches may react to pressure pulses within the pump. For example, if a wobble plate pump has three chambers, each rotation of the motor will cause three pressure pulses or pumping strokes. If the pressure switch reacts to a pressure pulse rather than the net operating fluid pressure at the outlet, unnecessary cycling will occur. Complex circuits and/or programming have been used in some applications to determine the net pressure and avoid unnecessary cycling, but this solution is often too complex and costly. Repeated cycling results in louder operation with the motor being energized and de-energized frequently. This is particularly undesirable in a non-industrial application, such as a pump in a recreational vehicle or in a home.